Non-aqueous inkjet ink composition and inkjet recording device

Abstract

The purpose of the present invention is to provide a non-aqueous inkjet ink composition and an inkjet recording device capable of suppressing missed ejection of a nozzle of a head. A non-aqueous inkjet ink composition for use in a recording method for printing for a long period of time without performing a nozzle leak response step, the non-aqueous inkjet ink composition containing a polymerizable monomer and a liquid photoinitiator that is liquid at 20 DEG C, the content of a solid photoinitiator that is solid at 20 DEG C being 1.5 mass% or less relative to the total amount of the non-aqueous inkjet ink composition.

Description

Technical Field

[0001] The present invention relates to a non-aqueous inkjet ink composition and an inkjet recording device. Background Art

[0002] The inkjet recording method can record high-definition images with a relatively simple device, and has been rapidly developed in various aspects. Among them, many studies have been conducted on the stability of continuous ejection. For example, Patent Document 1 discloses a radiation-curable inkjet composition, which contains a difunctional or higher acylphosphine oxide-based photopolymerization initiator and a polymerizable compound that are a single solid at room temperature, and the dissolved oxygen content of the composition is 0 to 8.0 kPa. The radiation-curable inkjet composition is contained in a composition container.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-199817 Summary of the invention

[0006] As disclosed in Patent Document 1, when preparing an inkjet composition containing a photopolymerization initiator that is solid at room temperature, ultrasonic treatment can be performed to dissolve fine particles of the photopolymerization initiator, or to remove dissolved oxygen contained in the inkjet composition, or to separate bubbles remaining inside or attached to the surface of the photopolymerization initiator particles from the photopolymerization initiator and release them into the composition, thereby removing tiny bubbles. However, without ultrasonic treatment, tiny bubbles will remain in the ink, resulting in the problem of increased nozzle leakage when recording is performed continuously for a long time.

[0007] As mentioned above, by applying an ultrasonic treatment process to the inkjet composition, tiny bubbles can be removed, but when the ultrasonic treatment process is performed, the placement location and structure of the manufacturing device of the inkjet composition are restricted, or the manufacturing process is time-consuming. Therefore, a method for preparing an ink that can perform long-term continuous recording without ultrasonic treatment is desired.

[0008] The present invention relates to a non-aqueous inkjet ink composition for use in a recording method for long-term printing without performing a nozzle leakage response process. The non-aqueous inkjet ink composition comprises a polymerizable monomer and a liquid photoinitiator that is liquid at 20°C, and the content of the solid photoinitiator that is solid at 20°C is less than 1.5% by mass relative to the total amount of the non-aqueous inkjet ink composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic cross-sectional view of a line-type printing press.

[0010] Figure 2 : is a table showing the results of the examples.

[0011] Figure 3 : is a table showing the results of the examples.

[0012] Figure 4 : is a table showing the results of the examples.

[0013] Figure 5 : is a table showing the results of the examples.

[0014] Description of Reference Numerals

[0015] 1…line printer, 110…feeding section, 120…conveying section, 130…recording section, 131…inkjet head, 132…light source, 133…light source, 140…drying section, 141…drying section, 142…drying section, 150…discharging section, F…recording medium, Y…conveying direction. DETAILED DESCRIPTION

[0016] Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited thereto and various modifications can be made without departing from the gist of the invention.

[0017] 1. Non-aqueous inkjet ink composition

[0018] The non-aqueous inkjet ink composition involved in this embodiment (hereinafter also referred to as "ink composition") is a non-aqueous inkjet ink composition used in a recording method for long-term printing without performing a nozzle leakage response process, comprising a polymerizable monomer and a liquid photoinitiator that is liquid at 20°C, and the content of the solid photoinitiator that is solid at 20°C is less than 1.5% by mass relative to the total amount of the above-mentioned non-aqueous inkjet ink composition.

[0019] Existing inkjet inks containing photoinitiators tend to have increased nozzle leakage when no ultrasonic treatment is applied. The main reasons are considered to be as follows. Existing inkjet inks containing photoinitiators use solid photoinitiators as photoinitiators from the perspective of curability. Therefore, when the ink is prepared, tiny bubbles will be generated in the inkjet ink. It is generally believed that if the inkjet ink that has generated these tiny bubbles is not subjected to an ultrasonic treatment process, the inkjet ink will be ejected from the inkjet head with tiny bubbles remaining, resulting in increased nozzle leakage in the head. Nozzle leakage means that due to the presence of bubbles in the ink near the nozzle, the ink cannot be properly ejected, resulting in nozzles that cannot be properly printed. However, the main reason for the increase in nozzle leakage in the head is not limited to this.

[0020] In particular, when printing is performed for a long time without performing the nozzle leakage countermeasure process, there is a tendency that the nozzle leakage of the head increases significantly. It is generally believed that this is because when printing is performed for a long time without performing the nozzle leakage countermeasure process, the tiny bubbles remaining in the inkjet ink are easily accumulated in the head. However, the main reason for the significant increase in the nozzle leakage of the head is not limited to this.

[0021] In addition, in order to suppress nozzle leakage of the head as described above, when an ultrasonic treatment process is applied to the existing inkjet ink containing a solid photoinitiator, it is necessary to set up equipment for the ultrasonic treatment process, which has the effect of limiting the placement location, structure, etc. of the inkjet ink manufacturing device and tends to extend the manufacturing time of the inkjet ink.

[0022] Therefore, in the present embodiment, by using a liquid photoinitiator that is liquid at 1 atmosphere and 20° C. as a photoinitiator, even if the ink composition is not subjected to ultrasonic treatment, it is possible to suppress nozzle leakage of the head without performing a nozzle leakage countermeasure process. It is generally believed that by using the above-mentioned liquid photoinitiator, it is difficult to generate fine bubbles when preparing the ink composition, but the main reason for suppressing nozzle leakage of the head is not limited to this. In addition, when preparing the ink composition, an ultrasonic treatment process is not required as when a solid photoinitiator is used, so the degree of freedom of the placement location and structure of the ink composition manufacturing device can be increased, and the manufacturing time of the ink composition can be shortened.

[0023] In addition, the ink composition of the present embodiment has a tendency to suppress nozzle leakage of the head even when printing for a long time without subjecting the ink composition to an ultrasonic treatment process and without performing a nozzle leakage countermeasure process. It is generally believed that this is because minute bubbles are not easily generated when preparing the ink composition, but the main reason why nozzle leakage of the head can be suppressed even when printing for a long time without subjecting the ink composition to an ultrasonic treatment process and without performing a nozzle leakage countermeasure process is not limited to this.

[0024] The viscosity of the ink composition at 25° C. is preferably less than 40 mPa·s, less than 30 mPa·s, less than 20 mPa·s, and is 3 to 40 mPa·s, 4 to 30 mPa·s, 5 to 25 mPa·s, or 10 to 20 mPa·s. By setting the viscosity of the ink composition within the above range, there is a tendency to obtain an ink composition suitable for inkjet recording methods.

[0025] The viscosity of the ink composition at 25° C. can be measured by a method in accordance with JIS Z 8803. The viscosity of the ink composition can be adjusted by changing the type and / or content of the photoinitiator, changing the type and / or content of the polymerizable monomer, changing the type and / or content of the oligomer, changing the type and / or content of the colorant, changing the type and / or content of the surfactant, adding a viscosity modifier as another component described later, and the like.

[0026] Hereinafter, each component of the ink composition according to the present embodiment will be described in detail.

[0027] 1.1. Photoinitiator

[0028] In this specification, "photoinitiator" includes sensitizers and fluorescent whitening agents used in conjunction with photopolymerization initiators. When the ink composition contains a photoinitiator, the photoinitiator generates active species (initiating species) such as free radicals, acids, and bases when irradiated with radiation, and the polymerization reaction of the polymerizable monomer described later is promoted by the function of the initiating species.

[0029] The photoinitiator of the present embodiment includes a liquid photoinitiator that is liquid at 1 atmosphere and 20°C (hereinafter, also referred to as "liquid photoinitiator" for short) and a solid photoinitiator that is fixed at 1 atmosphere and 20°C (hereinafter, also referred to as "solid photoinitiator" for short). The photoinitiator is not particularly limited, and examples thereof include: aromatic ketones, hydroxy ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thioxanthones, thiophene and other thio compounds, hexaarylbisimidazole compounds, ketoxime ester compounds, boric acid ester compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. These photoinitiators are used alone or in combination of two or more. In addition, examples of the photoinitiator of the present invention which is classified as a fluorescent whitening agent include naphthylbenzoxazolyl derivatives, thiophenebenzoxazolyl derivatives, distyrylbenzoxazolyl derivatives, coumarin derivatives, styrylbiphenyl derivatives, pyrazolone derivatives, distyryl derivatives, styryl derivatives of benzene and biphenyl, bis(indolizine-2-yl) derivatives, quinolones, naphthalimide, derivatives of dibenzothiophene-5,5'-dioxide, pyrene derivatives and pyridotriazole.

[0030] 1.1.1. Liquid photoinitiators

[0031] The ink composition of the present embodiment includes a liquid photoinitiator. As the liquid photoinitiator, in addition to the liquid photopolymerization initiator, a liquid sensitizer and a liquid fluorescent whitening agent can also be cited, which are not particularly limited, and can include, for example: aromatic ketones, hydroxy ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thioxanthones, thio compounds such as thiophene, hexaarylbisimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. Among them, it is preferred to use one or more selected from the group consisting of acylphosphine initiators and thioxanthone initiators, more preferably to use acylphosphine initiators, and further preferably to use acylphosphine initiators and thioxanthone initiators in combination. These liquid photoinitiators are used alone or in combination of two or more.

[0032] The content of the liquid photoinitiator is preferably 5.0 to 25.0 mass %, 7.0 to 22.5 mass %, 8.5 to 20.0 mass %, or 10.0 to 17.5 mass % relative to the total amount of the ink composition. When the content of the liquid photoinitiator is within the above range, there is a tendency for the curability and the suppression of nozzle leakage of the head to be more excellent.

[0033] The content of the liquid photoinitiator is preferably 80.0 to 99.9 mass %, 82.5 to 99.9 mass %, or 85.0 to 99.9 mass % relative to the total amount of the photoinitiator. Alternatively, the content of the liquid photoinitiator may be 100 mass % relative to the total amount of the photoinitiator. By making the content of the liquid photoinitiator within the above range, there is a tendency to have better curability and suppression of nozzle leakage of the head.

[0034] 1.1.1.1. Acylphosphine initiators

[0035] The ink composition of this embodiment may contain an acylphosphine-based initiator as an acylphosphine compound in a liquid photoinitiator. The acylphosphine-based initiator is not particularly limited, and examples thereof include ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (hereinafter also referred to as "TPO-L") or an oligomer thereof. Among them, ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate is preferred.

[0036] The content of the acylphosphine initiator is preferably 3.0 to 20.0 mass %, 5.0 to 15.0 mass %, 6.0 to 12.5 mass %, or 6.5 to 11.0 mass % relative to the total amount of the ink composition. When the content of the acylphosphine initiator is within the above range, the curing property and the suppression of nozzle leakage of the head tend to be more excellent.

[0037] The content of the acylphosphine initiator is preferably 30.0 to 99.0 mass%, 40.0 to 95.0 mass%, 45.0 to 90.0 mass%, 50.0 to 85.0 mass%, or 55.0 to 82.5 mass% relative to the total amount of the photoinitiator. When the content of the acylphosphine initiator is within the above range, there is a tendency for the curability and the suppression of nozzle leakage of the head to be more excellent.

[0038] The content of TPO-L is preferably 7.0% by mass or more, 7.0 to 20.0% by mass, 7.2 to 15.0% by mass, or 7.4 to 12.5% ​​by mass relative to the total amount of the ink composition. When the content of TPO-L is within the above range, curing properties tend to be more excellent.

[0039] 1.1.1.2. Thioxanthone-based initiators

[0040] The ink composition of this embodiment may further include a thioxanthone-based initiator as a thio compound in the liquid photoinitiator. The thioxanthone-based initiator is not particularly limited, and examples thereof include polybutylene glycol bis(9-oxo-9H-thioxanthenyloxy)acetate (CAS No. 813452-37-8), poly[oxy(methyl-1,2-ethylene)], α-hydro-ω-[[2-[(1-chloro-9-oxo-9H-thioxanthen-4-yl)oxy]acetyl]oxy]-, ether and 2,2-bis(hydroxymethyl)-1,3-propylene ester (4:1), i.e., Poly[oxy(methyl-1,2-ethanediyl)],

[0041] α-hydro-ω-[[2-[(1-chloro-9-oxo-9H-thioxanthen-4-yl)oxy]acetyl]oxy]-,ether with 2,2-bis(hydroxymethyl)-1,3-propanediyl(4:1)(CAS No.1003567-83-6). These thioxanthone-based initiators are used alone or in combination of two or more.

[0042] The content of the thioxanthone initiator is preferably 0.1 to 10.0 mass %, 0.5 to 7.5 mass %, or 1.0 to 5.0 mass % relative to the total amount of the ink composition. When the content of the thioxanthone initiator is within the above range, curing properties and suppression of nozzle leakage of the head tend to be more excellent.

[0043] In addition, when the ink composition is a transparent ink composition described later, the content of the thioxanthone-based initiator is preferably 3.0% by mass or less, 0.1 to 3.0% by mass, 0.1 to 2.0% by mass, or 0.1 to 1.0% by mass relative to the total amount of the transparent ink composition. When the content of the thioxanthone-based initiator is within the above range, there is a tendency that the curability and the yellowing of the coating film are more excellent.

[0044] The content of the thioxanthone initiator is preferably 1.0 to 40.0 mass %, 5.0 to 35.0 mass %, or 10.0 to 30.0 mass % relative to the total amount of the photoinitiator. When the content of the thioxanthone initiator is within the above range, curability and suppression of nozzle leakage of the head tend to be more excellent.

[0045] In addition, when the ink composition is a transparent ink composition described later, the content of the thioxanthone-based initiator is preferably 30.0% by mass or less, 1.0 to 30.0% by mass, 1.0 to 20.0% by mass, or 1.0 to 10.0% by mass relative to the total amount of the photoinitiator. When the content of the thioxanthone-based initiator is within the above range, there is a tendency for the curability, the suppression of nozzle leakage of the head, and the suppression of yellowing of the coating film to be more excellent.

[0046] 1.1.1.3. Other liquid photoinitiators

[0047] As other liquid photoinitiators, hydroxyketone-based photoinitiators can be mentioned. The hydroxyketone-based photoinitiators are not particularly limited, and examples thereof include 2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone or oligomers thereof.

[0048] The content of other liquid photoinitiators is not particularly limited, and is, for example, 0.1 to 10.0 mass %, 0.5 to 8.0 mass %, or 1.0 to 6.0 mass % relative to the total amount of the ink composition. In addition, other liquid photoinitiators may not be included.

[0049] The content of other liquid photoinitiators is not particularly limited, and is, for example, 0.1 to 40.0 mass %, 0.5 to 39.0 mass %, or 1.0 to 38.0 mass % relative to the total amount of the photoinitiators. In addition, other liquid photoinitiators may not be included.

[0050] 1.1.2. Solid photoinitiator

[0051] As solid photoinitiators, in addition to solid photopolymerization initiators, solid sensitizers and solid fluorescent whitening agents can be mentioned, which are not particularly limited, and examples thereof include aromatic ketones, hydroxy ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thioxanthones, thio compounds such as thiophene, hexaarylbisimidazole compounds, ketoxime ester compounds, boric acid ester compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds. These solid photoinitiators can be used alone or in combination of two or more.

[0052] The acylphosphine-based solid photoinitiator as the acylphosphine compound in the solid photoinitiator is not particularly limited, and examples thereof include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and diphenyl-2,4,6-trimethylbenzoylphosphine oxide (hereinafter also referred to as "TPO"). These acylphosphine-based solid photoinitiators are used alone or in combination of two or more.

[0053] Among the solid photoinitiators, the thioxanthone-based solid photoinitiator, which is a thio compound, is not particularly limited, and examples thereof include 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane.

[0054] In the ink composition of the present embodiment, the content of the solid photoinitiator is 1.50 mass % or less, preferably 0.50 mass % or less, 0.01 to 1.50 mass %, 0.01 to 1.00 mass %, 0.01 to 0.75 mass %, 0.01 to 0.50 mass %, 0.01 to 0.25 mass %, 0.01 to 0.10 mass % relative to the total amount of the ink composition. Alternatively, the ink composition of the present embodiment may not contain the solid photoinitiator. By setting the content of the solid photoinitiator within the above range, there is a tendency that the nozzle leakage of the head is more excellently suppressed.

[0055] The content of the solid photoinitiator is preferably 0.1 to 20.0 mass%, 0.1 to 15.0 mass%, 0.1 to 12.5 mass%, or 0.1 to 10.0 mass% relative to the total amount of the photoinitiator. Alternatively, the ink composition of the present embodiment may not contain a solid photoinitiator. By setting the content of the solid photoinitiator within the above range, there is a tendency that nozzle leakage of the head is more effectively suppressed.

[0056] 1.1.3. Photopolymerization initiator

[0057] The photopolymerization initiator of the present embodiment generates active species (initiating species) such as radicals, acids, and bases when irradiated with radiation, and promotes the polymerization reaction of the monomers by the function of the initiating species.

[0058] The liquid or solid photopolymerization initiator is not particularly limited, and examples thereof include ethyl phenyl (2,4,6-trimethylbenzoyl) phosphinate, 2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] acetone or its oligomers, phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide, and diphenyl-2,4,6-trimethylbenzoyl phosphine oxide. It should be noted that the photopolymerization initiator may be a liquid photoinitiator or a solid photoinitiator. The photopolymerization initiator may be used alone or in combination of two or more.

[0059] The content of the photopolymerization initiator is not particularly limited, and is, for example, 2.0 to 25.0 mass %, 3.0 to 20.0 mass %, 4.0 to 17.5 mass %, or 5.0 to 15.0 mass % relative to the total amount of the ink composition.

[0060] The content of the photopolymerization initiator is not particularly limited, and is, for example, 60.0 to 100.0 mass %, 65.0 to 97.5 mass %, or 70.0 to 95.0 mass % relative to the total amount of the photoinitiator.

[0061] 1.1.4. Fluorescent brightener

[0062] The ink composition of this embodiment may include a fluorescent whitening agent as a photoinitiator. The fluorescent whitening agent of this embodiment has the function of absorbing ultraviolet rays and emitting blue-white fluorescence. In addition, since the fluorescent whitening agent shows a sensitizing effect by combining with other photoinitiators, the inclusion of the fluorescent whitening agent tends to have better curability than when only the photoinitiator is included.

[0063] Liquid or solid fluorescent whitening agents are not particularly limited, and examples thereof include naphthoxybenzoxazolyl derivatives, thiophenebenzoxazolyl derivatives, distyrylbenzoxazolyl derivatives, coumarin derivatives, styrylbiphenyl derivatives, pyrazolone derivatives, distyryl derivatives, styryl derivatives of benzene and biphenyl, bis(indolizine-2-yl) derivatives, quinolone, naphthalimide, derivatives of dibenzothiophene-5,5'-dioxide, pyrene derivatives, and pyridotriazole, etc. These fluorescent whitening agents are used alone or in combination of two or more.

[0064] More specifically, the fluorescent whitening agent is not particularly limited, and examples thereof include 1,4-bis(2-benzoxazolyl)naphthalene and 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene. It should be noted that the fluorescent whitening agent may also be a liquid photoinitiator or a solid photoinitiator. The fluorescent whitening agent may be used alone or in combination of two or more.

[0065] The content of the fluorescent brightener is preferably 1.00 mass % or less, 0.50 mass % or less, 0.01 to 1.00 mass %, 0.03 to 0.75 mass %, or 0.05 to 0.50 mass % relative to the total amount of the ink composition. When the content of the fluorescent brightener is within the above range, there is a tendency for the curability and low-temperature precipitation properties to be more excellent.

[0066] The content of the fluorescent whitening agent is preferably 0.1 to 10.0 mass %, 0.3 to 7.5 mass %, or 0.5 to 5.0 mass % relative to the total amount of the photoinitiator. When the content of the fluorescent whitening agent is within the above range, the curing property tends to be more excellent.

[0067] 1.1.5. Sensitizer

[0068] The sensitizer of the present embodiment has a function of absorbing radiation to become excited, and promoting the decomposition of the photopolymerization initiator by contacting the photopolymerization initiator, thereby further promoting the polymerization reaction of the monomer.

[0069] The liquid or solid sensitizer is not particularly limited, and examples thereof include: amine compounds (aliphatic amines, amines containing aromatic rings, piperidine, reaction products of epoxy resins and amines, triethanolamine triacrylate, etc.), urea compounds (allylthiourea, o-tolylthiourea, etc.), sulfur compounds (2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, sodium diethyldithiophosphate, soluble salts of aromatic sulfinic acids, etc.), nitrile compounds (N,N-diethyl-p-aminobenzonitrile, etc.), phosphorus compounds (tri-n-butylphosphine, sodium diethyldithiophosphate, etc.), nitrogen compounds (Michler's ketone, N-nitrosohydroxylamine derivatives, oxazolidine compounds, tetrahydro-1,3-oxazine compounds, condensates of formaldehyde or acetaldehyde and diamines, etc.), chlorine compounds (carbon tetrachloride, hexachloroethane, etc.), etc. These fluorescent whitening agents are used alone or in combination of two or more. It should be noted that the sensitizer may be a liquid photoinitiator or a solid photoinitiator. The sensitizer may be used alone or in combination of two or more.

[0070] The content of the sensitizer is not particularly limited, and is, for example, 0.5 to 10.0% by mass, 1.0 to 8.0% by mass, or 2.0 to 6.0% by mass relative to the total amount of the ink composition. Alternatively, the sensitizer may not be contained.

[0071] The content of the sensitizer is not particularly limited, and is, for example, 1.0 to 40.0 mass %, 5.0 to 35.0 mass %, or 10.0 to 30.0 mass % relative to the total amount of the photoinitiator. Alternatively, the sensitizer may not be contained.

[0072] 1.2. Polymerizable monomers

[0073] The ink composition of this embodiment includes a polymerizable monomer. The polymerizable monomer is not particularly limited, and is, for example, a photopolymerizable compound that polymerizes and cures when irradiated with light such as ultraviolet rays. Examples of the polymerizable monomer include monofunctional monomers, difunctional monomers, and trifunctional or higher polyfunctional monomers. The polymerizable monomers are used alone or in combination of two or more.

[0074] The content of the polymerizable monomer is preferably 60.0 to 95.0 mass %, 62.5 to 92.5 mass %, 65.0 to 90.0 mass %, or 67.5 to 87.5 mass % relative to the total amount of the ink composition. When the content of the polymerizable monomer is within the above range, flexibility, adhesion, and curability tend to be more excellent.

[0075] 1.2.1. Monofunctional monomers

[0076] The monofunctional monomer is not particularly limited, and examples thereof include benzyl (meth)acrylate, isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxy Polyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, lactone-modified flexible (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, dicyclopentane (meth) acrylate, cyclic trimethylolpropane formal (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate and vinylmethyl oxazolidinone. Among them, from the viewpoint of improving adhesion and curability, vinylmethyl oxazolidinone is preferred. These monofunctional monomers are used alone or in combination of two or more.

[0077] The content of the monofunctional monomer is preferably 25.0 to 57.5 mass %, 27.5 to 55.0 mass %, or 30.0 to 52.5 mass % relative to the total amount of the ink composition. When the content of the monofunctional monomer is within the above range, there is a tendency for the adhesion and curability to be more excellent.

[0078] The content of the monofunctional monomer is preferably 25.0 to 70.0 mass %, 27.5 to 67.5 mass %, or 30.0 to 65.0 mass % relative to the total amount of the polymerizable monomers. When the content of the monofunctional monomer is within the above range, there is a tendency for the adhesion and curability to be more excellent.

[0079] In addition, the ink composition of the present embodiment preferably contains 30% by mass or less of phenoxyethyl (meth) acrylate as a monofunctional monomer relative to the total amount of the ink composition. Phenoxyethyl (meth) acrylate preferably contains 25% by mass or less, preferably contains 15% by mass or less, preferably contains 10% by mass or less, and preferably contains 5% by mass or less. In addition, phenoxyethyl (meth) acrylate may not be contained. In addition, the lower limit of the content of phenoxyethyl (meth) acrylate is not particularly limited, for example, it is 1% by mass or more, 2% by mass or more, or 3% by mass or more relative to the total amount of the ink composition. By containing 30% by mass or less of phenoxyethyl (meth) acrylate or not containing phenoxyethyl (meth) acrylate, there is a tendency to have excellent continuous printing stability and low temperature precipitation. In addition, there is also a tendency to prevent the coating of the inkjet ink composition from yellowing, reduce the viscosity of the inkjet ink composition, and make the ejection stability excellent.

[0080] The content of vinylmethyloxazolidinone is preferably 5.0 to 30.0 mass %, 7.5 to 27.5 mass %, or 10.0 to 25.0 mass % relative to the total amount of the ink composition. When the content of vinylmethyloxazolidinone is 5.0 mass % or more, there is a tendency for better adhesion, and when the content of vinylmethyloxazolidinone is 30.0 mass % or less, there is a tendency for better curability.

[0081] 1.2.2. Difunctional monomers

[0082] The bifunctional monomer is not particularly limited, and examples thereof include diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A EO (ethylene oxide) adduct di(meth)acrylate, bisphenol A PO (propylene oxide) adduct di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, and a vinyl ether group-containing (meth)acrylate represented by the following formula (1). Among them, vinyl ether group-containing (meth)acrylates represented by the following formula (1) are preferred from the viewpoint of improving viscosity characteristics, flexibility, and curability. These bifunctional monomers are used alone or in combination of two or more.

[0083] H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ···(1)

[0084] In the formula, R 1 is a hydrogen atom or a methyl group, R 2 is a divalent organic residue having 2 to 20 carbon atoms, R 3 It is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.

[0085] In the above formula (1), R 2 The divalent organic residue having 2 to 20 carbon atoms represented by : may include: a linear, branched or cyclic, optionally substituted alkylene group having 2 to 20 carbon atoms, an optionally substituted alkylene group having 2 to 20 carbon atoms and having an oxygen atom derived from an ether bond and / or an ester bond in the structure, and an optionally substituted divalent aromatic group having 6 to 11 carbon atoms. Among them, preferred are alkylene groups having 2 to 6 carbon atoms such as vinyl, n-propenyl, isopropenyl and butenyl, and alkylene groups having 2 to 9 carbon atoms and having an oxygen atom derived from an ether bond in the structure such as oxyvinyl, oxyn-propenyl, oxyisopropenyl and oxybutenyl. Furthermore, from the viewpoint of being able to further reduce the viscosity of the composition and making the curability of the composition better, a compound having a glycol ether chain is more preferred, wherein R 2 It is an alkylene group having 2 to 9 carbon atoms and having an oxygen atom derived from an ether bond in its structure, such as oxyvinyl, oxy-n-propenyl, oxy-isopropenyl and oxy-butenyl.

[0086] In the above formula (1), R 3 The monovalent organic residue having 1 to 11 carbon atoms represented by the above-mentioned group is preferably a linear, branched or cyclic, optionally substituted alkyl group having 1 to 10 carbon atoms, or an optionally substituted aromatic group having 6 to 11 carbon atoms. Among them, an alkyl group having 1 to 2 carbon atoms such as a methyl group or an ethyl group, and an aromatic group having 6 to 8 carbon atoms such as a phenyl group and a benzyl group are preferably used.

[0087] In the case where each of the above-mentioned organic residues is an optionally substituted group, the substituent is divided into a group containing carbon atoms and a group not containing carbon atoms. First, in the case where the above-mentioned substituent is a group containing carbon atoms, the carbon atom is recorded in the number of carbon atoms of the organic residue. As the group containing carbon atoms, for example, carboxyl and alkoxy can be mentioned, but it is not limited to this. Next, as the group not containing carbon atoms, for example: hydroxyl group and halo group can be mentioned, but it is not limited to this.

[0088] Specific examples of the compound of formula (1) include, but are not particularly limited to, 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, 2-methyl-3-vinyloxypropyl (meth)acrylate, 1,1-dimethyl-2-vinyloxyethyl ester, 3-vinyloxybutyl (meth)acrylate, 1-methyl-2-vinyloxypropyl (meth)acrylate, 2-vinyloxybutyl (meth)acrylate, 4-vinyloxycyclohexyl (meth)acrylate, 6-vinyloxyhexyl (meth)acrylate, 4-vinyloxymethylcyclohexylmethyl (meth)acrylate, 3-vinyloxymethylcyclohexylmethyl (meth)acrylate, 2-vinyloxymethylcyclohexylmethyl (meth)acrylate, p-vinyloxymethylphenylmethyl (meth)acrylate, m-vinyloxymethylphenylmethyl (meth)acrylate, o-vinyloxymethylphenyl (meth)acrylate Methyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(vinyloxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy) isopropoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyethoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)isopropyl acrylate, 2-(vinyloxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenyloxyethoxy)ethyl (meth)acrylate, 2-(isopropenyloxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenyloxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenyloxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenyloxyethoxyethoxyethoxy)ethyl (meth)acrylate, polyethylene glycol monovinyl (meth)acrylate, and polypropylene glycol monovinyl (meth)acrylate. Among these specific examples, 2-(2-vinyloxyethoxy)ethyl acrylate is particularly preferred from the viewpoints of viscosity characteristics, flexibility, and curability. It should be noted that, in the present embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate is sometimes referred to as VEEA. ,

[0089] The content of the difunctional monomer is preferably 20.0 to 65.0 mass %, 25.0 to 62.5 mass %, or 30.0 to 60.0 mass % relative to the total amount of the ink composition. When the content of the difunctional monomer is within the above range, the viscosity characteristics, flexibility, and curability tend to be more excellent.

[0090] The content of the difunctional monomer is preferably 25.0 to 75.0 mass %, 30.0 to 72.5 mass %, or 35.0 to 70.0 mass % relative to the total amount of the polymerizable monomers. When the content of the difunctional monomer is within the above range, the viscosity characteristics, flexibility, and curability tend to be more excellent.

[0091] The content of 2-(2-vinyloxyethoxy)ethyl acrylate is preferably 10.0 to 40.0 mass %, 12.5 to 37.5 mass %, or 15.0 to 35.0 mass % relative to the total amount of the ink composition. When the content of 2-(2-vinyloxyethoxy)ethyl acrylate is 10.0 mass % or more, the viscosity characteristics and curability tend to be more excellent, and when the content of 2-(2-vinyloxyethoxy)ethyl acrylate is 40.0 mass % or less, the flexibility tends to be more excellent.

[0092] 1.2.3. Multifunctional monomers

[0093] The polyfunctional monomer having three or more functions is not particularly limited, and examples thereof include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerol propoxy tri(meth)acrylate, taurolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate. These polyfunctional monomers may be used alone or in combination of two or more.

[0094] The content of the polyfunctional monomer is preferably 1.0 to 10.0% by mass, 2.0 to 7.5% by mass, or 3.0 to 5.0% by mass relative to the total amount of the ink composition. When the content of the polyfunctional monomer is within the above range, the viscosity characteristics tend to be more excellent.

[0095] The content of the polyfunctional monomer is preferably 1.0 to 10.0 mass %, 2.0 to 9.0 mass %, or 3.0 to 8.0 mass % relative to the total amount of the polymerizable monomers. When the content of the polyfunctional monomer is within the above range, the viscosity characteristics tend to be more excellent.

[0096] 1.3. Oligomers

[0097] The ink composition of this embodiment may contain an oligomer. The oligomer of this embodiment refers to a polymer such as a dimer or trimer having a polymerizable compound as a constituent component, and is a compound having one or more polymerizable functional groups. It should be noted that the polymerizable compound mentioned here is not limited to the above-mentioned monofunctional monomer, difunctional monomer, and polyfunctional monomer.

[0098] Such an oligomer is not particularly limited, and examples thereof include a urethane acrylate oligomer whose repeating structure is urethane, a polyester acrylate oligomer whose repeating structure is ester, and an epoxy acrylate oligomer whose repeating structure is epoxy.

[0099] Among them, polyurethane acrylate oligomers are preferred, aliphatic polyurethane acrylate oligomers and aromatic polyurethane acrylate oligomers are more preferred, and aliphatic polyurethane acrylate oligomers are further preferred. In addition, polyurethane acrylate oligomers are preferably polyurethane acrylate oligomers with a functional group number of less than four functions, and more preferably polyurethane acrylate oligomers with a functional group number of two functions. It should be noted that the functional group number represents the functional group number of the (meth)acryloyl group.

[0100] The urethane acrylate oligomer is not particularly limited, and examples thereof include polyether urethane acrylate oligomers having a urethane bond and an ether bond, polyester urethane acrylate oligomers having a urethane bond and an ester bond, and polycarbonate urethane acrylate oligomers having a urethane bond and a carbonate bond.

[0101] Examples of commercially available polyurethane oligomers include CN929 (polyester-based aliphatic polyurethane acrylate, functional group number 3), CN962 (polyester-based aliphatic polyurethane acrylate, functional group number 2), CN963 (polyester-based aliphatic polyurethane acrylate, functional group number 2), CN964 (polyester-based aliphatic polyurethane acrylate, functional group number 2), CN965 (polyester-based aliphatic polyurethane acrylate, functional group number 2), CN968 (polyester-based aliphatic polyurethane acrylate, functional group number 6), CN980 (polyether-based aliphatic polyurethane acrylate, functional group number 2), CN981 (polyester-based aliphatic polyurethane acrylate, functional group number 2), and CN982 (polyester-based aliphatic polyurethane acrylate, functional group number 2). ester acrylate, functional group number 2), CN982 (polyester aliphatic urethane acrylate, functional group number 2), CN983 (polyester aliphatic urethane acrylate, functional group number 2), CN996 (polyether aliphatic urethane acrylate, functional group number 2), CN9001 (polyester aliphatic urethane acrylate, functional group number 2), CN9002 (polyester aliphatic urethane acrylate, functional group number 2), CN9788 (polyester aliphatic urethane acrylate, functional group number 2), CN9893 (polyether aliphatic urethane acrylate, functional group number 2) (the above are Sartomer Company), EBECRYL 230 (functional group number 2), 270 (functional group number 2), 5129 (functional group number 6), 8210 (functional group number 4), 8301 (functional group number 6), 8311 (functional group number 3), 8402 (functional group number 2), 8405 (functional group number 4), 8701 (functional group number 3), 8804 (functional group number 2), 8807 (functional group number 2), 9260 (functional group number 3), 9270 (functional group number 2), KRM 8200 (functional group number 6), 8296 (functional group number 3), 8452 (functional group number 10) (all of the above are trade names of DAICEL-CYTEC Company LTD.), and aromatic urethane acrylate oligomers such as CN971 (polyester-based aromatic urethane acrylate, functional group number 3), CN972 (polyester-based aromatic urethane acrylate, functional group number 3), CN975 (polyester-based aromatic urethane acrylate, functional group number 6), CN978 (polyester-based aromatic urethane acrylate, functional group number 2), CN9782 (polyester-based aromatic urethane acrylate, functional group number 2), CN9783 (polyester-based aromatic urethane acrylate, functional group number 2) (these are trade names manufactured by Sartomer), EBECRYL 210 (functional group number 2), 220 (functional group number 6) (these are trade names manufactured by DAICEL-CYTEC), but are not limited to these.

[0102] The content of the oligomer is not particularly limited, and is, for example, 0.1 to 10.0% by mass, 0.5 to 7.5% by mass, or 1.0 to 7.0% by mass relative to the total amount of the ink composition.

[0103] 1.4. Pigment

[0104] The ink composition of the present embodiment may or may not contain a colorant. When a colorant is contained, examples of the colorant include dyes and pigments.

[0105] The dye is not particularly limited, and examples thereof include acid dyes, direct dyes, reactive dyes, and basic dyes. Specific examples of the dye include CI Acid Yellow 17, 23, 42, 44, 79, 142, CI Acid Red 52, 80, 82, 249, 254, 289, CI Acid Blue 9, 45, 249, CI Acid Black 1, 2, 24, 94, CI Food Black 1, 2, CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 14 2, 144, 173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, CI Reactive Black 3, 4, 35. These dyes are used alone or in combination of two or more.

[0106] The pigment is not particularly limited, and examples thereof include inorganic pigments and organic pigments. The inorganic pigment is not particularly limited, and examples thereof include carbon blacks such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide. The organic pigment includes azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelated azo pigments, phthalocyanine pigments, perylene and pyrene pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and polycyclic pigments such as quinophthalone pigments, dye chelating agents, dye lakes, nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments. These pigments are used alone or in combination of two or more.

[0107] The carbon black is not particularly limited, and examples thereof include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by Carbon Columbia), Rega 400R, Rega 1330R, Rega 1660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (all manufactured by Cabot Corporation). JAPAN KK), ColorBlack FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color BlackFW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, PrintexU, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, Special Black 4 (all manufactured by Degussa).

[0108] The white pigment is not particularly limited, and examples thereof include CI Pigment White 6, 18, and 21.

[0109] The yellow pigment is not particularly limited, and examples thereof include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, and 180.

[0110] The magenta pigment is not particularly limited, and examples thereof include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57:1, 8 8, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or CI Pigment Violet 19, 23, 32, 33, 36, 38, 43, 50.

[0111] The cyan pigment is not particularly limited, and examples thereof include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Vat Blue 4 and 60.

[0112] Pigments other than magenta, cyan and yellow are not particularly limited, and examples thereof include CI Pigment Green 7, 10, CI Pigment Brown 3, 5, 25, 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, and 63.

[0113] The content of the colorant is not particularly limited, and is, for example, 1.0 to 5.0% by mass relative to the total amount of the ink composition.

[0114] Alternatively, the ink composition of the present embodiment may be a transparent ink composition. A transparent ink composition refers to an ink composition that does not contain or substantially does not contain a colorant. In the present embodiment, “substantially does not contain a colorant” is not particularly limited, for example, the content of the colorant is 0.50% by mass or less, 0.25% by mass or less, 0.10% by mass or less, 0.05% by mass or less, 0.01% by mass or less, 0.001 to 0.500% by mass, 0.001 to 0.250% by mass, 0.001 to 0.100% by mass, 0.001 to 0.050% by mass, 0.001 to 0.010% by mass relative to the total amount of the ink composition.

[0115] When the ink composition of the present embodiment is a clear ink composition, by including a thioxanthone-based initiator as the liquid photoinitiator and a fluorescent whitening agent, yellowing of the coating film can be suppressed and curability can be improved.

[0116] 1.4.1. Dispersants

[0117] As the dispersant for dispersing the pigment, it is not particularly limited, and for example, it can be cited: a dispersant with one or more of polyoxyalkylene polyamine, vinyl polymer and copolymer, acrylic polymer and copolymer, polyester, polyamide, polyimide, polyurethane, amino polymer, silicon-containing polymer, sulfur-containing polymer, fluorine-containing polymer and epoxy resin as the main component. As a commercially available dispersant, it can be cited: ADISPER series made by Ajinomoto Fine-Techno, Solsperse series (Solsperse 36000 (acid value 45), Solsperse 32000 (amine value 35) etc.) available from Avecia Co., DISPERBYK series (DISPERBYK 168, 180 etc.) made by BYKChemie, DISPARLON series made by Kusumoto Chemical Co., Ltd. These dispersants are used alone or in combination of two or more.

[0118] The content of the dispersant is not particularly limited, and is, for example, 0.1 to 3.0% by mass relative to the total amount of the ink composition.

[0119] 1.5. Surfactants

[0120] The surfactant is not particularly limited, and examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants. From the viewpoint of more effectively and reliably achieving the effects of the present invention, silicone-based surfactants are preferred.

[0121] The silicone-based surfactant is not particularly limited, and examples thereof include BYK-UV3500, UV3570, and BYK350 (trade names of BYK-Chemie Japan Ltd.).

[0122] The content of the surfactant is not particularly limited, and may be, for example, 0.1 to 1.0% by mass relative to the total amount of the ink composition.

[0123] 1.6. Inhibitors

[0124] The polymerization inhibitor is not particularly limited, and examples thereof include hydroquinone, hydroquinone monomethyl ether (MEHQ), 1-o-2,3,5-trimethylhydroquinone, and hydroquinone represented by 2-tert-butylhydroquinone; catechol, 4-methylcatechol, and catechol represented by 4-tert-butylcatechol; phenol, butylhydroxytoluene, butylhydroxyanisole, p-methoxyphenol, cresol, pyrogallol, 3,5-di-tert-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-tert-butylphenol), Phenols represented by (4-ethyl-6-butylphenol) and 4,4'-thiobis(3-methyl-6-tert-butylphenol); hindered amines represented by compounds having a 2,2,6,6-tetramethylpiperidine-N-oxyl skeleton represented by 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, compounds having a 2,2,6,6-tetramethylpiperidine skeleton, compounds having a 2,2,6,6-tetramethylpiperidine-N-alkyl skeleton, and compounds having a 2,2,6,6-tetramethylpiperidine-N-acyl skeleton. These polymerization inhibitors are used alone or in combination of two or more.

[0125] The content of the polymerization inhibitor is not particularly limited, and may be, for example, 0.05 to 1.0% by mass relative to the total amount of the ink composition. When the content of the polymerization inhibitor is within the above range, the storage stability of the ink tends to be more excellent.

[0126] 1.7. Water

[0127] The non-aqueous inkjet ink composition involved in this embodiment does not contain or substantially does not contain water. In this embodiment, "substantially does not contain water" is not particularly limited, and for example, the content of water is 0.50% by mass or less, 0.25% by mass or less, 0.10% by mass or less, 0.05% by mass or less, or 0.01% by mass or less relative to the total amount of the ink composition. In addition, for example, it is 0.001 to 0.500% by mass, 0.001 to 0.250% by mass, 0.001 to 0.100% by mass, 0.001 to 0.050% by mass, or 0.001 to 0.010% by mass, but is not particularly limited.

[0128] In the present specification, when simply referred to as water, there is no particular limitation, and examples thereof include ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water.

[0129] 1.8. Other ingredients

[0130] The ink composition of this embodiment may contain other known components that can be used in the ink composition in addition to the above components. The other components are not particularly limited, and examples thereof include lubricants, dissolution aids, viscosity modifiers, pH modifiers, antioxidants, preservatives, and antiseptics. These other components may be used alone or in combination of two or more.

[0131] 2. Method for producing non-aqueous inkjet ink composition

[0132] The method for producing the non-aqueous inkjet ink composition of the present embodiment is not particularly limited, and for example, the above-mentioned components may be mixed. In addition, in the method for producing the ink composition of the present embodiment, a pigment and a dispersant as a colorant may be dispersed in a monomer to prepare a colorant dispersion, and the obtained colorant dispersion may be mixed with the above-mentioned components. It should be noted that the monomer is not limited to the above-mentioned polymerizable monomer.

[0133] The colorant dispersion may be prepared before preparing the ink composition, or may be prepared by mixing and dispersing the colorant dispersion simultaneously with other components during the preparation of the ink composition.

[0134] 3. Recording medium

[0135] The recording medium used for recording with the ink composition of the present embodiment is not particularly limited, and examples thereof include absorptive recording media, low-absorptive recording media, and non-absorptive recording media.

[0136] The absorptive recording medium is not particularly limited, and examples thereof include ordinary paper such as electronic photographic paper with high ink permeability, inkjet paper (inkjet paper having an ink absorbing layer composed of silica particles and alumina particles, or inkjet-specific paper having an ink absorbing layer composed of hydrophilic polymers such as polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), cloth, etc.

[0137] The low-absorption recording medium is not particularly limited, and examples thereof include coated paper, art paper, cast-coated paper, and the like used for ordinary offset printing, which have low ink permeability.

[0138] The non-absorbent recording medium is not particularly limited, and examples thereof include: films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; plates of metals such as iron, silver, copper, and aluminum; or metal plates and plastic films of the above various metals, plates of alloys such as stainless steel and brass manufactured by vapor deposition; recording media in which plastic films such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane are bonded (coated) onto a paper substrate, etc.

[0139] 4. Inkjet recording method

[0140] The inkjet recording method of the present embodiment (hereinafter, also referred to as "recording method") includes an ink attaching step of ejecting the ink composition of the present embodiment from an inkjet head and attaching it to a recording medium, and an irradiation step of irradiating the ink composition attached to the recording medium with radiation, and may also include other steps such as a conveying step of conveying the recording medium as required. In addition, the recording method of the present embodiment does not include a nozzle leakage response step for preventing nozzle leakage of the head.

[0141] The recording method of the ink composition of the present embodiment is a method for printing for a long time without performing a nozzle leakage countermeasure process. When using a common ink containing a solid photoinitiator, a large number of recorded objects can be efficiently produced by printing for a long time without performing a nozzle leakage countermeasure process, but there is a tendency that the nozzle leakage of the head increases significantly. However, by using the ink composition of the present embodiment, when printing for a long time without performing a nozzle leakage countermeasure process, there is a tendency that a large number of recorded objects can be efficiently produced while suppressing the nozzle leakage of the head.

[0142] It should be noted that, here, "long time" means, for example, printing for several minutes or seconds, going through the nozzle leakage response process, and then printing for several minutes or seconds, etc., and does not include short-time printing. As for the purpose of stipulating "long time", as an example, it is to stipulate the following situations: long-term printing without performing the nozzle leakage response process while conveying the recording medium as in a line printer; and long-term printing without performing the nozzle leakage response process even in a serial printer when the carriage carrying the head moves to the end of the recording medium.

[0143] Based on such a viewpoint, in the present embodiment, if "long time" is defined numerically, it means more than 10 minutes. In addition, preferably more than 20 minutes, more preferably more than 30 minutes, more preferably more than 40 minutes, more preferably more than 50 minutes. The upper limit is not particularly limited, and it is less than 24 hours, less than 18 hours, less than 12 hours, less than 6 hours, and less than 3 hours.

[0144] In addition, "printing without performing a nozzle leakage response process" is not particularly limited, and for example, printing without performing a nozzle leakage response process such as pressurized nozzle cleaning, suction nozzle cleaning, and flushing during printing. Although a large number of recorded objects can be efficiently produced by printing without performing a nozzle leakage response process, there is a tendency that the nozzle leakage of the head increases significantly. However, by using the ink composition of this embodiment, when printing without performing a nozzle leakage response process, there is a tendency that a large number of recorded objects can be efficiently produced while suppressing the nozzle leakage of the head.

[0145] 4.1. Ink adhesion process

[0146] In the ink attachment step, the ink composition of the present embodiment is ejected from the inkjet head and attached to the recording medium. More specifically, the pressure generating means provided in the inkjet head is driven to eject the ink composition filled in the pressure generating chamber of the inkjet head from the nozzle.

[0147] Examples of the inkjet head used in the ink adhesion step include a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0148] In the line method using a line head, for example, an inkjet head having a width greater than the recording width of a recording medium is fixed to a recording device. Then, the recording medium and the inkjet head are relatively moved in a sub-scanning direction (a conveying direction of the recording medium, i.e., a direction orthogonal to the width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with the movement, thereby recording an image on the recording medium.

[0149] In the serial method using a serial head, for example, an inkjet head is mounted on a carriage that is movable in the width direction of a recording medium. Then, the carriage is moved in the main scanning direction (the width direction of the recording medium), and ink droplets are ejected from the nozzles of the inkjet head in conjunction with the movement, thereby recording an image on the recording medium.

[0150] The ink adhesion step of the present embodiment may be performed for a long time without performing the nozzle leakage countermeasure step. In this case, the long time is not particularly limited and is, for example, the same as the definition in the recording method of the ink composition of the present embodiment.

[0151] In addition, “performing the ink attaching step without performing the nozzle leakage countermeasure step” means, for example, attaching the ink composition to the recording medium without performing the nozzle leakage countermeasure step, and is not particularly limited.

[0152] The step of reducing the oxygen concentration by introducing nitrogen may be included in the ink adhesion step. This step tends to improve the curability of the ink composition, improve the adhesion and abrasion resistance of the recorded material, or reduce odor. In addition, the amount of photoinitiator added to the ink composition tends to be reduced.

[0153] 4.2. Irradiation process

[0154] In the irradiation step, the ink composition attached to the recording medium is irradiated with radiation. After irradiation with radiation, the monomer begins to undergo polymerization reaction, and the composition is cured to form a coating film. At this time, when a photoinitiator is present, active species (initiating species) such as free radicals, acids and bases are generated, and the polymerization reaction of the monomer is promoted by the function of the initiating species.

[0155] Among them, as the radiation, ultraviolet rays, infrared rays, visible rays, X-rays, etc. can be cited. As the radiation source, the composition is irradiated by a radiation source arranged downstream of the inkjet head. As the radiation source, there is no particular limitation, and for example, UV-LED can be cited. By using such a radiation source, it is possible to achieve miniaturization of the device and reduce costs. Since the UV-LED as the ultraviolet source is small, it can be installed in the inkjet recording device.

[0156] 4.3. Nozzle leakage response process

[0157] The recording method of the present embodiment does not include a nozzle leakage countermeasure step. By using the ink composition of the present embodiment, there is a tendency that nozzle leakage of the head can be suppressed even when a nozzle leakage countermeasure step is not included.

[0158] The nozzle leakage response process is not particularly limited, and examples thereof include: pressurized nozzle cleaning, suction nozzle cleaning, and flushing. It is possible to discharge or remove bubbles existing near the nozzle from the nozzle, thereby preventing nozzle leakage. It is difficult to obtain the effect of responding to nozzle leakage by wiping the ink ejection surface of the nozzle, and therefore it is not included in the nozzle leakage response process.

[0159] 4.4. Transport process

[0160] The recording method of this embodiment may include a conveying process. In the conveying process, the recording medium is conveyed in a predetermined direction in the recording device. More specifically, a conveying roller or a conveying belt provided in the recording device is used to convey the recording medium from the paper feeding section to the paper discharging section of the recording device. During the conveying process, the ink composition ejected from the inkjet head adheres to the recording medium to form a recorded object. The order and timing of performing the ink adhesion process, the irradiation process, the nozzle leakage response process, and the conveying process are not particularly limited. For example, the four processes may be performed simultaneously or alternately. In addition, some of the four processes may be performed simultaneously, and the remaining processes may be performed separately.

[0161] 5. Recording device

[0162] The inkjet recording device of the present embodiment is not particularly limited, and a serial printer, for example, can be cited. In the case of a serial printer, as an inkjet head, a head having a length less than the width of the recording medium is provided, and the head moves to record in multiple passes. In addition, in a serial printer, a head is mounted on a carriage moving in a specified direction, and the head moves with the movement of the carriage, thereby ejecting an ink composition on the recording medium. Thus, recording is performed in more than 2 passes. It should be noted that the pass is also referred to as the main scan. A sub-scan for conveying the recording medium is performed between passes. That is, the main scan and the sub-scan are performed alternately.

[0163] The inkjet recording apparatus of the present embodiment is not particularly limited, and a line-type printer may be mentioned, for example. Figure 1 A schematic cross-sectional view of a printing press in a row mode is shown in FIG. Figure 1 As shown, the line printer 1 includes a recording medium feeding unit 110 , a conveying unit 120 , a recording unit 130 , a drying unit 140 , and a discharging unit 150 .

[0164] Here, the feed unit 110 feeds the recording medium F to the conveying unit 120, and the conveying unit 120 conveys the recording medium F sent from the feed unit 110 to the recording unit 130, the drying unit 140, and the discharge unit 150. Specifically, the conveying unit 120 has conveying rollers, and conveys the sent recording medium F in the conveying direction Y.

[0165] In addition, the recording unit 130 includes an inkjet head 131 for ejecting a radiation-curable composition onto the recording medium F sent from the conveying unit 120, and light sources 132 and 133 for irradiating the attached composition with radiation. In the case of a line-type printer, for example, as the inkjet head 131, a line head having a length equal to or longer than the width of the recording medium is provided, and the head is fixed and does not (almost not) move, and recording is performed in one pass (single pass). A pass is also referred to as a scan.

[0166] In this embodiment, the conveying speed of the recording medium and the distance between the inkjet head 131 and the light source 132 are adjusted so that the above-mentioned recording method can be performed. Figure 1 Although one inkjet head is shown in the figure, the invention is not limited thereto and a plurality of inkjet heads may be provided depending on the type of composition.

[0167] The drying section 140 is used to dry the composition attached to the recording medium as needed, and includes a drying section 141 (platen heater) disposed opposite to the recording section 130 and a drying section 142 disposed downstream of the recording section 130. In addition, the discharge section 150 is disposed so as to be able to discharge the recorded matter to the outside of the line printer 1. When drying is not necessary, the drying section 141 may not be provided.

[0168] In addition, the inkjet recording device of the present embodiment is not limited to the above-mentioned serial printing machine, and can also be the above-mentioned line printing machine. The line printing machine refers to, for example, a printing machine as follows: a line head having an inkjet head having a length greater than the recording width of the recording medium, and a moving mechanism that moves the recording medium and the inkjet head relative to each other in a direction orthogonal to the width direction of the recording medium, and records the recording medium by a single scan. Compared with the serial printing machine, the line printing machine can print continuously for a long time, so a large number of recorded objects can be efficiently manufactured, but there is a tendency that the nozzle leakage of the head increases significantly. However, by using the ink composition of the present embodiment, in the case of long-term continuous printing, there is a tendency that a large number of recorded objects can be efficiently manufactured while suppressing the nozzle leakage of the head.

[0169] The inkjet recording apparatus of the present embodiment may further include a control unit configured to execute a recording method for printing for a long period of time (for example, 10 minutes or more) without performing a nozzle leakage countermeasure step.

[0170] Example

[0171] The present invention will be described in detail below using Examples and Comparative Examples. The present invention is not limited to the following Examples at all. Unless otherwise specified, all reactions were performed at room temperature (25° C.) and 1 atmosphere.

[0172] 1. Preparation of non-aqueous inkjet ink composition

[0173] First, the pigment, dispersant, and base monomer are weighed and placed in a tank for dispersing the pigment, and a ceramic bead mill with a diameter of 1 mm is added to the tank and stirred to obtain a pigment dispersion in which the pigment is dispersed in the base monomer. Figures 2 to 5 The colorant dispersion and the remaining components were added to a mixing tank as a stainless steel container in the manner of the composition described in , mixed and stirred at 25° C. for 2 hours, and then filtered through a 5 μm membrane filter to obtain the non-aqueous inkjet ink composition of the embodiment and the comparative example. It should be noted that, unless otherwise specified, the numerical value of each component shown in each example in the figure represents the content (mass %).

[0174] Figures 2 to 5 The abbreviations used in the product and the ingredients are as follows. Figures 2 to 5 A blank column indicates that the ingredient is not used. Figures 2 to 5 In the table, “-” means that the evaluation was not conducted.

[0175] PB15:3 (CI Pigment Blue 15:3)

[0176] ·Carbon black (trade name "MA-100", manufactured by Mitsubishi Chemical Corporation)

[0177] Dispersant 1 (trade name "Solsperse 36000", manufactured by Avecia)

[0178] Dispersant 2 (trade name "Solsperse 32000", manufactured by Avecia)

[0179] PEA (trade name "VISCOAT #192", manufactured by Osaka Organic Chemical Industry Co., Ltd., phenoxyethyl acrylate)

[0180] · BZA (trade name "VISCOAT #160", manufactured by Osaka Organic Chemical Industry Co., Ltd., benzyl acrylate)

[0181] IBXA (Isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0182] CTFA (trade name "VISCOAT #200", manufactured by Osaka Organic Chemical Industry Co., Ltd., cyclic trimethylolpropane formal acrylate)

[0183] ·VMOX (manufactured by BASF, vinylmethyloxazolidinone)

[0184] ·4-HBA (manufactured by Osaka Organic Chemical Industry Co., Ltd., 4-hydroxybutyl acrylate)

[0185] ·VEEA (manufactured by Nippon Shokubai Co., Ltd., 2-(2-vinyloxyethoxy)ethyl acrylate)·

[0186] DPGDA (trade name "VISCOAT #310HP", manufactured by Osaka Organic Chemical Industry Co., Ltd., tripropylene glycol diacrylate)

[0187] 16HDDA (trade name "VISCOAT #230", manufactured by Osaka Organic Chemical Industry Co., Ltd., 1,6-hexanediol diacrylate)

[0188] ·A-DPH (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., dipentaerythritol hexaacrylate)

[0189] CN9893 (manufactured by Sartomer, difunctional polyurethane acrylate oligomer)

[0190] ·Omnirad TPO-L (manufactured by IGM Resins BV, ethyl phenyl (2,4,6-trimethylbenzoyl) phosphinate: acylphosphine series)

[0191] ESACURE KIP 150 (manufactured by IGM Resins BV, oligomer of 2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone: hydroxyketone series)

[0192] Speedcure 7010 (manufactured by Sartomer, CAS No. 1003567-83-6: thioxanthone-based)

[0193] ·Omnipol TX (manufactured by IGM Resins BV, CAS No. 813452-37-8: thioxanthone-based)

[0194] ·Omnirad 819 (manufactured by IGM Resins BV, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide: acylphosphine type)

[0195] ·Omnirad TPO (manufactured by IGM Resins BV, diphenyl-2,4,6-trimethylbenzoylphosphine oxide: acylphosphine type)

[0196] Speedcure DETX (manufactured by Sartomer, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane: thioxanthone-based)

[0197] ·TELALUX KCB (manufactured by Clariant Japan, 1,4-bis(2-benzoxazolyl)naphthalene: solid at 1 atm and 20°C)

[0198] ·TELALUX OB (manufactured by Clariant Japan Co., Ltd., 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene: solid at 1 atm and 20°C)

[0199] BYK-UV3500 (manufactured by BYK Additives & Instruments, polyether-modified polydimethylsiloxane having an acrylic group)

[0200] LA-7RD (manufactured by ADEKA Corporation, 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl radical)

[0201] ·MEHQ (trade name "p-methoxyphenol", manufactured by Kanto Chemical Co., Ltd., hydroquinone monomethyl ether)

[0202] 2. Evaluation Method

[0203] Figures 2 to 5 In the table, a “-” indicates that the evaluation was not conducted.

[0204] 2.1. Viscosity characteristics (initial viscosity of ink)

[0205] The viscosity of the ink compositions of Examples and Comparative Examples just prepared was measured at room temperature (25° C.) using a rotational viscometer (product name: “Rheometer MCR-301”, manufactured by Anton Paar) in accordance with JIS Z 8803.

[0206] [Evaluation criteria]

[0207] A: The viscosity is lower than 20 mPa·s.

[0208] B: The viscosity is 20 mPa·s or more and less than 30 mPa·s.

[0209] C: The viscosity is 30 mPa·s or more and less than 40 mPa·s.

[0210] D: The viscosity is 40 mPa·s or more.

[0211] 2.2. Continuous printing stability

[0212] Prepare a line-type inkjet printer, wherein the nozzle diameter of the inkjet head is 20 μm, the driving frequency of the ejection is 15 kHz, and the amount of ink ejected each time is adjusted to 7 ng, and each head has 360 nozzles. Continuous ejection is performed from the head (360 nozzles) according to the above ejection frequency. Check every 5 minutes whether ink is ejected from all nozzles, and the maximum total continuous ejection is 50 minutes. It should be noted that nozzle cleaning and flushing are not performed during this period.

[0213] [Evaluation criteria]

[0214] A: There was no nozzle that did not spray during 50 minutes of continuous spraying.

[0215] B: No nozzles failed to eject during continuous ejection for 20 minutes.

[0216] C: There is a nozzle that does not eject when the continuous ejection lasts for less than 20 minutes.

[0217] 2.3. Curing

[0218] The ink composition of the examples and comparative examples was applied to a substrate in an amount that gave a film thickness of 8 μm (film thickness after curing), and the curing energy required for curing was confirmed. The substrate was wiped with a cotton swab, and the state of the cotton swab was used to determine whether the substrate was cured. The LED with a peak wavelength of 395 nm was used for irradiation, and the curing energy was determined by 1100 mW / cm 2The substrate used was a PET film (PET50A PL SIN [trade name], manufactured by Lintec). The irradiated coating film (composition film) was rubbed 10 times with a cotton swab under a load of 100 g to determine the curing energy (irradiation energy) at the time when it was no longer scratched.

[0219] It should be noted that the irradiation intensity [mW / cm 2 ], and the irradiation energy [mJ / cm 2 The irradiation intensity was measured using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by KONICA MINOLTA SENSING, INC.).

[0220] [Evaluation criteria]

[0221] AA: The curing energy at the point of no scratching is 200 mJ / cm 2 the following.

[0222] A: The curing energy at the point of no scratching exceeds 200mJ / cm 2 And 300mJ / cm 2 the following.

[0223] B: The curing energy at the point of no scratching exceeds 300mJ / cm 2 And 400mJ / cm 2 the following.

[0224] C: The curing energy at the point of no scratching exceeds 400mJ / cm 2 .

[0225] 2.4. Softness

[0226] The ink composition of the embodiment and comparative example was applied to a PET film (PET50A PL SIN [trade name], manufactured by Lintec) in an amount that made the film thickness reach 8 μm (film thickness after curing), and irradiated with radiation under the same conditions as the curability evaluation until the time point when there was no more scratches, so that the ink composition of the embodiment and comparative example was cured to make a cured film on the PET film. The cured film was peeled off from the PET film and cut into strips with a width of 1 cm and a length of 8 cm to make a test piece. The tensile tester (TENSILON, manufactured by ORIENTEC) was used to evaluate the elongation of the test piece. The elongation is the value at the time point when cracks occur when stretched at 5 mm / min. This value is calculated according to {(length at the time of cracking - length before extension) / length before extension × 100}.

[0227] [Evaluation criteria]

[0228] A: The elongation is 100% or more.

[0229] B: The elongation ratio is 50% or more and less than 100%.

[0230] C: The elongation is less than 50%.

[0231] 2.5. Adhesion

[0232] The ink compositions of the examples and comparative examples were applied to a PET film (PET50A PL SIN [trade name], manufactured by Lintec) in an amount such that the film thickness reached 8 μm (film thickness after curing), and irradiated with radiation under the same conditions as in the curability evaluation until no scratches were observed, thereby curing the ink compositions of the examples and comparative examples to produce recorded materials. The recorded materials were evaluated by the cross-hatch method in accordance with JIS K5600-5-6.

[0233] More specifically, a cutter is used to abut the blade of the cutting tool in a perpendicular manner relative to the coating film, and a grid with a distance of 1 mm between the cuts is cut to make 10×10 grids. A transparent adhesive tape (width 25 mm) with a length of about 75 mm is pasted on the grid, and it is rubbed with fingers to be able to see the cured film through. Then, within 5 minutes of pasting the tape, it takes 0.5 to 1.0 seconds to reliably tear off the tape from the cured film at an angle close to 60°, and the state of the grid is observed by visual inspection. The evaluation criteria are as follows.

[0234] [Evaluation criteria]

[0235] A: No peeling occurred in any of the 10×10 grid sections.

[0236] B: 1 to 10 of 10×10 grid sections were peeled off.

[0237] C: 11 to 50 of the 10×10 grids were peeled off.

[0238] D: 51 or more of 10×10 grid sections were peeled off.

[0239] 2.6. Low temperature precipitation

[0240] 40 g of the ink composition of the examples and comparative examples was placed in a 50 mL glass bottle and left at -20°C for 48 hours. The mixture was then returned to room temperature (25°C) and filtered through a 10 μm filter. Foreign matter on the filter was visually observed.

[0241] [Evaluation criteria]

[0242] A: There are multiple foreign objects on the filter.

[0243] B: There is a little foreign matter on the filter.

[0244] C: There is no foreign matter on the filter.

[0245] 2.7. Evaluation of color tone of transparent ink composition

[0246] A 10 μm coating film of the ink composition of the example was prepared using a bar coater, and cured by irradiation with radiation in such a manner that the energy reached twice the curing energy at the time point when no scratches were made in the curability evaluation. Next, the cured coating film was colorimetrically measured using a colorimeter "Spectrolino" manufactured by GretagMacbeth, and the b* after the measurement was used for evaluation. The larger the b*, the more yellow the coating film.

[0247] [Evaluation criteria]

[0248] A: b*<1

[0249] B: 1≤b*<2

[0250] C: 2≤b*

[0251] 3. Evaluation results

[0252] according to Figures 2 to 5 The evaluation results show that, compared with the ink composition of the comparative example, the ink composition of the example suppresses nozzle leakage of the head and is excellent in continuous printing stability.

Claims

1. A non-aqueous inkjet ink composition, characterized in that A recording method for long-term printing without performing a nozzle leak response process. Containing a polymerizable monomer and a liquid photoinitiator which is liquid at 20°C, The content of the solid photoinitiator which is solid at 20° C. is 1.5% by mass or less based on the total amount of the non-aqueous inkjet ink composition.

2. The non-aqueous inkjet ink composition according to claim 1, wherein The content of the solid photoinitiator is 0.5% by mass or less relative to the total amount of the non-aqueous inkjet ink composition.

3. The non-aqueous inkjet ink composition according to claim 1, wherein The solid photoinitiator contains a fluorescent brightener, and the content of the fluorescent brightener is 0.5 mass % or less relative to the total amount of the non-aqueous inkjet ink composition.

4. The non-aqueous inkjet ink composition according to claim 1, wherein The liquid photoinitiator comprises an acylphosphine-based initiator.

5. The non-aqueous inkjet ink composition according to claim 4, wherein The acylphosphine-based initiator includes ethyl phenyl (2,4,6-trimethylbenzoyl) phosphinate.

6. The non-aqueous inkjet ink composition according to claim 5, wherein The content of ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate is 7% by mass or more based on the total amount of the non-aqueous inkjet ink composition.

7. The non-aqueous inkjet ink composition according to claim 4, wherein The liquid photoinitiator further comprises a thioxanthone-based initiator.

8. The non-aqueous inkjet ink composition according to claim 1, wherein The polymerizable monomer includes 2-(2-vinyloxyethoxy)ethyl acrylate, The content of the 2-(2-vinyloxyethoxy)ethyl acrylate is 10 to 40% by mass based on the total amount of the non-aqueous inkjet ink composition.

9. The non-aqueous inkjet ink composition according to claim 1, wherein The polymerizable monomer comprises vinylmethyloxazolidinone, The content of the vinylmethyloxazolidinone is 5 to 30% by mass based on the total amount of the non-aqueous inkjet ink composition.

10. The non-aqueous inkjet ink composition according to claim 1, wherein The non-aqueous inkjet ink composition is a transparent ink composition.

11. An inkjet recording device, characterized in that: have: an inkjet head having a width greater than a recording width of a recording medium; and a moving mechanism for relatively moving the recording medium and the inkjet head in a direction orthogonal to the width direction of the recording medium, The inkjet head discharges the nonaqueous inkjet ink composition according to any one of claims 1 to 11 toward the recording medium.

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